The present invention realtes to a method and apparatus for joining two members together in a manner to permit relative movement therebetween, and more particularly to such a method and apparatus for mounting a sun visor to an automobile body.
For a number of years it has been a common practice to manufacture automobile sun visors from plastic. These visors are mounted to the automobile at the location of the front window, and the visor has an edge portion by which it is attached to the automobile body at spaced locations around the front window. A common method for attaching the visor to the automobile is to drill a plurality of matching holes through the visor and the automobile body at spaced locations along the fastening edge of the sun visor. Blind rivets are placed one in each pair of holes, and the forward or blind side of the rivet is expanded in a conventional manner by withdrawing an interior expanding member of the rivet, while pressing a flange of the rivet against the visor.
One of the problems with fastening the sun visor to the automobile body in this manner is that due to temperature changes, there is expansion and contraction of the plastic visor relative to the metal car body. The resulting stresses sometimes cause cracks to form in the visor. There have been some attempts in the prior art to alleviate this problem by providing certain tolerances in the fit of the fastener relative to the holes in the automobile body and the visor. However, this solution has not been entirely satisfactory since in some instances the rigid fastening of a visor to the automobile body still will sometimes cause cracks in the visor.
A search of the patent literature has disclosed a number of fastening devices, these being listed below.
U.S. Pat. No. 3,930,432 discloses a bolt head having a washer element that fits against the bearing face of the bolt head. The combination of the washer and the cover is to protect the fastening device against corrosion and also to provide a decorative effect. The patent states that this type of fastener can be used to attach the trim to a vehicle.
British Specification No. 890,049 shows a similar arrangement where there is a collar that fits against the head of a screw. The screw is used to fasten a mirror to a wall and the function of the collar is to provide a cushion between the head and the surface of the mirror. This is to avoid the problem of the screw pressing too strongly against the mirror so as to cause cracking thereof.
British Specification No. 1,116,444 shows a fastening device where there is a washer and cap assembly covering the head of a screw. The particular application is to attach corrugated sheeting to the walls and roof of building structures. The cap and washer assembly is to provide resistance against corrosion and to provide a seal against moisture.
U.S. Pat. No. 4,123,630 is representative of a fastening device where there is provided spacing between a shank of some member and the structure to which it is mounted.
In view of the foregoing, it is an object of the present invention to provide a method and apparatus for fastening a sun visor to an automobile, in a manner to alleviate the problem of cracking of the sun visor due to differential expansion and construction of the sun visor relative to the automobile body.